feat: backend support for creating and storing service accounts (#22698)

Add is_service_account column to users table with CHECK constraints
enforcing login_type='none' and empty email for service accounts.
Update user creation API to validate service account constraints.

Related to:
https://linear.app/codercom/issue/PLAT-27/feat-backend-support-for-creating-and-storing-service-accounts

coderd/database/dump.sql

@@ -1471,7 +1471,10 @@ CREATE TABLE users (
     hashed_one_time_passcode bytea,
     one_time_passcode_expires_at timestamp with time zone,
     is_system boolean DEFAULT false NOT NULL,
+    is_service_account boolean DEFAULT false NOT NULL,
     CONSTRAINT one_time_passcode_set CHECK ((((hashed_one_time_passcode IS NULL) AND (one_time_passcode_expires_at IS NULL)) OR ((hashed_one_time_passcode IS NOT NULL) AND (one_time_passcode_expires_at IS NOT NULL)))),
+    CONSTRAINT users_email_not_empty CHECK (((is_service_account = true) = (email = ''::text))),
+    CONSTRAINT users_service_account_login_type CHECK (((is_service_account = false) OR (login_type = 'none'::login_type))),
     CONSTRAINT users_username_min_length CHECK ((length(username) >= 1))
 );
 
@@ -1487,6 +1490,8 @@ COMMENT ON COLUMN users.one_time_passcode_expires_at IS 'The time when the one-t
 
 COMMENT ON COLUMN users.is_system IS 'Determines if a user is a system user, and therefore cannot login or perform normal actions';
 
+COMMENT ON COLUMN users.is_service_account IS 'Determines if a user is an admin-managed account that cannot login';
+
 CREATE VIEW group_members_expanded AS
  WITH all_members AS (
          SELECT group_members.user_id,
@@ -3601,7 +3606,7 @@ CREATE INDEX idx_user_deleted_deleted_at ON user_deleted USING btree (deleted_at
 
 CREATE INDEX idx_user_status_changes_changed_at ON user_status_changes USING btree (changed_at);
 
-CREATE UNIQUE INDEX idx_users_email ON users USING btree (email) WHERE (deleted = false);
+CREATE UNIQUE INDEX idx_users_email ON users USING btree (email) WHERE ((deleted = false) AND (email <> ''::text));
 
 CREATE UNIQUE INDEX idx_users_username ON users USING btree (username) WHERE (deleted = false);
 
@@ -3651,7 +3656,7 @@ CREATE UNIQUE INDEX user_secrets_user_file_path_idx ON user_secrets USING btree
 
 CREATE UNIQUE INDEX user_secrets_user_name_idx ON user_secrets USING btree (user_id, name);
 
-CREATE UNIQUE INDEX users_email_lower_idx ON users USING btree (lower(email)) WHERE (deleted = false);
+CREATE UNIQUE INDEX users_email_lower_idx ON users USING btree (lower(email)) WHERE ((deleted = false) AND (email <> ''::text));
 
 CREATE UNIQUE INDEX users_username_lower_idx ON users USING btree (lower(username)) WHERE (deleted = false);